1. Field of the Invention
The invention relates to a communication device for the transmission of information signals via transmission lines having a central coupling arrangement with associated line assemblies, where a xe2x80x9c1:Nxe2x80x9d redundancy group comprising N active line assemblies and a standby line assembly allows one of the N active line assemblies to be switched to standby via a selection device.
2. Description of the Related Art
Depending on the required reliability against Different redundancy assemblies associated with a communication device, depending on the required reliability against failure for this device. Examples of these redundancy structures are xe2x80x9c1+1xe2x80x9d, xe2x80x9c1:1xe2x80x9d and xe2x80x9c1:Nxe2x80x9d line assembly redundancy, as is described in xe2x80x9cIEEE Journal on Selected Areas in Communicationsxe2x80x9d Vol. 15, No. 5, June 1997, pages 795 to 806. In the case of a xe2x80x9c1+1xe2x80x9d redundancy structure, two line assemblies are operated in parallel, in order to transmit information signal streams over them in a redundant manner. In this situation, however, only one of these redundant information signal streams is considered for further processing.
In the case of xe2x80x9c1:1xe2x80x9d line assembly redundancy, only one of two line assemblies is used as the active line assembly; a changeover is made to the remaining line assembly, which is used as a standby assembly, only if a fault occurs in the active line assembly.
Finally, in the case of xe2x80x9c1:Nxe2x80x9d line assembly redundancy, a single standby line assembly is provided in addition to a plurality N of line assemblies. If a fault occurs on one of the N line assemblies, the standby line assembly is then used instead of this line assembly.
In the case of xe2x80x9c1:Nxe2x80x9d line assembly redundancy, a selector arrangement is generally connected between the line assemblies and the external transmission lines. This selector arrangement can distribute the individual transmission lines between the N line assemblies and the standby line assembly. This prior art will be described in more detail below, in conjunction with FIG. 1. However, it is noted that if such a selector arrangement fails, or when this selector arrangement is replaced as a result of such a failure, all of the transmission lines connected to it, and thus the connections running via it, are interrupted.
The object of the present invention is to provide a way in which a communication device can be designed for the transmission of information signals via transmission lines having a central coupling arrangement with associated line assemblies, where a xe2x80x9c1:Nxe2x80x9d redundancy group comprising N active line assemblies and a standby line assembly allows one of the N active line assemblies to be switched to standby via a selection device, in order to improve the reliability against failure over the above prior art when using xe2x80x9c1:Nxe2x80x9d line assembly redundancy.
In the case of the above communication device, this object is achieved by the selection device of a respective xe2x80x9c1:Nxe2x80x9d redundancy group having N signal connections on a first connection side, and only one individual signal connection on a second connection side that is connected to the standby line assembly, and where line-specific switches are inserted into each of the transmission lines that selectively connect the respective transmission line via a first switching path to the active line assembly associated with it, or via a second switching path to one of the N signal connections of the selection device, and where the selection device and the N switch can be controlled such that, in the normal mode, the N transmission lines are connected directly via the first switching paths of the line-specific switch to the N active line assemblies, while, when one of the N active line assemblies is in the standby mode, its associated transmission line is connected via the second switching path of the associated switch and the selection device to the standby line assembly.
The invention results in the advantage that, by designing and arranging the selection device and switch within a xe2x80x9c1:Nxe2x80x9d redundancy group, this selection device can be replaced during normal operation of the communication device without adversely affecting the normal operation. When the communication device is in the standby mode, replacement of the selection device affects only the transmission path which is currently switched to standby.
Advantageous refinements of the invention result when the communications device is designed as an ATM communication device which operates using an asynchronous transfer mode and allows the transmission of information signals in the course of virtual connections, and where the coupling arrangement is assigned a central control device that controls setting up and clearing of virtual connections. An advantage may also be found when the central control device is designed such that it can control the selection device and the line-specific switch of the respective xe2x80x9c1:Nxe2x80x9d redundancy group.
The selection device may also have test loops for each of the N signal connections which, in the normal mode, each allow the insertion of one test loop from and to the coupling arrangement. The central control device can also be designed so that it effectuates a controls of both the insertion of the associated test loop, and then the conduct of a loop test, to be controlled individually for the test loop.
The adjacent line assemblies of a xe2x80x9c1:Nxe2x80x9d redundancy group can be connected to one another via a control line for emitting a fault message, and the line assemblies may be designed in such a manner that they emit, upon receipt of such a fault message, a control signal which requires the activation of a standby mode to the central control device. Finally, the line-specific switches may be implemented in the form of a PIN diode switch.